A novel method to extract vanadium and chromium from vanadium slag using molten <scp><scp>NaOH</scp>‐<scp>NaNO</scp></scp>₃ binary system

A new method using NaOH‐NaNO 3 binary melts to treat vanadium slag is proposed. Vanadium and chromium can be simultaneously extracted in the leaching processes. Under the optimum reaction conditions, the recovery of vanadium and chromium can reach 93.7% and 88.2% in 6 h, respectively. The kinetics investigation indicates that the decomposition of vanadium slag is controlled by mass transfer in product layer. During the reaction, NaOH is believed to provide basic media and facilitate the dissolution of acidic oxides. NaNO 3 decomposes to produce a large amount of active oxygen species, such as O, , and O 2− . NaOH intensifies the decomposition of NaNO 3 to NaNO 2 , but inhibits further decomposition of NaNO 2 . NaNO 3 can be regenerated by oxidation of NaNO 2 using oxygen at high temperature. The apparent activation energy of NaNO 2 oxidation in the temperature ranging from 350 to 450°C is 105.5 kJ/mol. © 2012 American Institute of Chemical Engineers AIChE J, 59: 541–552, 2013